The present invention relates to a method of retracting a head of a hard disc device when trouble occurs and particularly, to a method of detecting a short circuit of a terminal on the side that supplies a current to a VCM.
In a hard disc device, when some anomaly occurs, it is necessary to protect the device and data. In such a case, it is necessary to retract a head over a medium to a predetermined position by operating a VCM (Voice Coil Motor) driver.
However, of output lines VCM(+) and VCM(−) of the VCM driver, when the line corresponding to the source side of a retract current is short-circuited to the ground, it is no longer possible to retract the head. Further, a voltage is applied to the line short-circuited to the ground as a result, therefore, there is a possibility of the destruction of the VCM driver by an unexpectedly high current.
Japanese Patent Laid-Open No. 2004-86982 (Patent Document 1) discloses that when the power source is shut off in the magnetic disc storage device, the head is retracted both safely and quickly.
It is also possible to employ another method of retracting a head by sensing an overcurrent. As this method, there is a method of simultaneously detecting a current to a spindle motor and a current the VCM driver causes to flow to the VCM.